Means for phase discrimination of an alternating current signal



Dec. 16, 1958 H. PERNICK MEANS FOR PHASE DISCRIMINATION OF AN ALTERNATING CURRENT SIGNAL Filed Nov. 30, 1954 2 Sheets-Sheet 1 TIME CONTROLLED IMPEDANCE TIME CONTROLLED IMPEDANCE REF SOURCE PHASING NETWORK REF SOURCE SOURCE FIG. 5

INVE/VTUR Henry L. Pernicfi Dec. 16, 1958 MEANS Filed Nov. 30, 1954 H. L. PERNICK FOR PHASE DISCRIMINATION OF AN ALTERNATING CURRENT SIGNAL 2 Sheets-Sheet 2 REF SOURCE REF SOURCE n "K/T FIG, 6

FIG. 4

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ATTORNEY mANS FOR PHASE DISCRIMINATION OF AN .ALTERNATING CURRENT SIGNAL phase quadraturecomponent from an applied wave supplied'by" an alternating-current. source l, and passing an Henry L Perniclr', New York, N. Y., assignor, by mesne assignments, to United Aircraft Corporation, East Hartford, Conn, a corporation of Delaware Ap lication November 30, 1954, SerialNo."472,121

' 7 Claims. c1. 250-27 This invention relates to a phase discriminator circuit and particularly to a circuit capable of selecting a desired phase component from an applied wave.

Morep'articularly, the invention relates to a circuit which'utilizes a reference source toselect the desired phase component from the applied wave. i

Phase discriminator circuits which are capable of selecting'the in-phase component or phase quadrature component from'an applied wave, have founduse in many systems; "One example, is the alternating-current servo mechanism system which employs servo amplifiers. The two phase servo motor which the amplifier ordinarily feeds'in such'a system will develop'torque only if the Fig. 7- shows the progress of the applied wave in the circuit a's' the phase quadrature component 'is selected "1 therefrom.

Fig. 1 illustrates the general embodiment of the phase":-

Patented Dec. 16, 1958 discriminator circuit capable of selecting the in-phaseor energy-component representative of the selected phase component to'theoutputterminals 2.

The alternating current'waye isappliedtto a first time controlled impedance 3 which blocks or attenuates a pre- 1 determined-portion of each cycle. The portion blocked depends on the component to be selected. For example, if it is desired'to select the iii-phase component of the alternating wave, then ;the time controlled impedance 3- 6 together with capacitor 5 produce a negligible phase amplifier output is in quadrature with themotor fixed field 1 excitation. 'Amplifier output signals not possessingthe above phase relationship consequently produce no useful" effect and in fact increase heat'dis'sipation in the motor.

Furthermore, allowing such signals to passthrough the amplifier, may cause saturation of the amplifier stages and impair the ability of the amplifier to transmit the desired signals.

Phase discriminator circuits are often required'in' resolver test work where it is necessary to measure the in-pha'se and/or quadrature components. Also, in the multiplex transmission of a plurality of signals' over-a pair of lines, information may be carried by in-phase and phase quadrature signals, and detected by in-phas'e and phase quadrature discriminators.

Accordingly, it is an object of this invention to provide a phase discriminator circuit which is extremely simple and capable of performing each of the above-mentioned functions.

In accordance with an aspect of my invention, there is provided a phase discriminator circuit for selecting a desired phase component fronran input wave having a given frequency. A discrete part of each cycle, containing the desired phase component, is applied to a storage device, e. g. a capacitor, which eifectively shifts part of the stored energy to the remainingpart of each cycle. The energy in the remaining part of the cycle which may be of a finite or zero value, is representative of the desired phasecomponent and is selected atthe output of the discriminator circuit.

The above-mentioned and other features and objects of this invention and the manner of attaining them will become more apparent, and the invention itself will be best understood by reference to the following description of an embodiment of the invention taken in connection with the accompanying drawings, wherein:

Fig. 1 is a schematic diagram of a generic embodiment i of the invention;

shift. Thus, the average energy stored in capacitor 5 during the application of the unblocked portion of the cycle,

indicated at X, is derived from the capacitor 5 during that part of the cycle initially blocked and indicated at Y. In other words, the average energy stored in capacitor 5 is shifted fromfthe unblocked portion of the cycle to the initially blocked portion of the cycle.

The waveform as'derived from the capacitor 5 is ap pliedto a second time-controlled impedance 7 which is timedto block or attenuate the other half of thecycle and thereby pass to the output 2 the' Wave form shownat Fig. 6D. The energy'cornponent, appearing at the output of 1 the circuit is representative of the in-phase component Figure 7 illustrates the action of the circuitin suppressing the undesired phase component of the signal. The

undesired signal in this case is the quadrature phase componentof the input signal 1.

The quadrature-phase wave is shown at Fig. 7A and the blocked wave form is shown at Fig. 7B, the unblocked portion being shown at P. Since the wave form P is symmetrical and has no direct currentcomponent it is unaifected by the capacitor 5 and the wave form at the output thereof is indicated by Fig. 7C. Timely operation of impedance 7 blocks the first part of the cycle thereby passing zeroenergy to the output 2 as'indicated by Fig. 7D. 5

Thus, the energy component representative of the phase quadrature component is zero.

If it is desired to select the in-phase component, the

impedances are operatedas described above; however,

' if it is desired to select the phase quadrature component,

the impedances are operated out of phase with re- 5 spect to the phase of the applied wave. For example, for phase quadrature selection, impedance 3 is operated to block one half cycle of the wave when it is 90 out of phase with the applied wave.

The desired phase component is selected by the timely operation'bf the impedances 3 and 7, and by utilizing the energy displacing characteristic of a storagedevice,

such as a capacitor. Thus, by operating one impedance during one half cycle and the other impedance during the other half cycle, the complete cycle is sequentially blocked. However, the discrete energy value derived at the output of the circuit is produced only forinput signal components that are in-phase with the time controlled impedance switching.

As has been explained hereinabove, the impedance 3 provides a means for applying a predetermined portion of the input signal to amplifier 4. It will be understood that capacitor 5 provides a high pass filtering action for the amplified predetermined portion of the input signal with the result that a periodic wave form includ ing no direct current component is fed to the impedance 7. The impedance 7 eliminates from this periodic wave form a portion corresponding to the predetermined signal. ,7

portion to produce an output representative of the desired phase component of the input signal.

Of the many suitable forms of time controlled impedances which should be apparent to one skilled in the art, three satisfactory circuits are shown by Figs, 2, 3 and 4.

Referring to Fig. 2, a mechanical switch indicated at 8 is used as the time-controlled impedance. The switch 8 comprises an armature 9 movable between two terminals 10 and 11. Terminal 10 is coupled to the'input, and terminal 11 to the output, of capacitor 5. A reference source 12 is provided which generates a wave having the same frequency as the applied wave. Coupled to the reference source 12 is a phasing network 13 which controls the time of operation of armature 9. For example, if the in-phase components are to be selected, the armature 9 will be in the position shown during the first half of the cycle from 0 to 1r, thereby permitting the wave to be applied unattenuated to the capacitor 5. During the period fl'OHlJI to 21r,ih6 phasing network actuates the armature 9 to make contact with terminal 10 thereby passing that portion of the cycle to ground. The sequence of operation is repeated with each cycle. If it is desired to select the phase-quadrature component, the phasing network simply delays the time of operating the armature 9 by the period 1r/2.

In Fig. 3, the time-controlled impedance devices comprise triodes 14, 15 and 16, 17 respectively. triodes is necessary for each impedance switch. impedance switch the cathode and anode of one triode are coupled respectively to the anode and cathode of the other, and the junctions thereof are coupled respectively to ground and either to the amplifier input or output of capacitor 5, depending on the location of the switch.

A reference source 18 of biasing voltage is coupled to the grids of the tubes 14, 15 and a similar reference source 19 is coupled to the grids of tubes 16 and 17.

The sources 18 and 19 drive the grids to effect the switching action required to produce the wave forms shown by Figs. 6 and 7. For example, Figures 5A and 5B are the waveforms of reference sources 19 and 18 respectively that would be required to select an in-phase signal component.

Fig. 5A is the wave form of the biasing potential. applied by source 18 to tubes 14 and 15, and Fig. 5B is the wave form of biasing potential applied by source 19 to the tubes 16 and 17. The negative portion of the biasing potential applied by the sources is sufiicient to cut off the tubes to which it is applied. For example, if it is desired to select the in-phase component (Fig. 6) during the period from 0 to 1r the output energy from the capacitor 5 is positive, therefore tube 16 conducts and passes that portion of the cycle to ground. During the period from 1r to 211-, the applied wave is negative and tube 15 conducts shunting that portion of the cycle to ground. If it is desired to select the phase quadrature components, the reference signals must be shifted in phase by 90 from those shown on Figures 5A and 5B A pair of In each i out departing from the spirit of the invention.

In Fig. 4, the time-controlled impedances comprise diodes 20, 21, and 22, 23 respectively. The anode of diode 20, and the cathode of diode 21 are coupled to the input of amplifier 4, and the anode of diode 22 and the cathode of diode 23 are coupled to the output of capacitor 5. The cathode of diode 22 is coupled to the anodeof diode 21 and the junction thereof is coupled to one terminal of given polarity, of a reference source 24; and, the anode of diode 23 is coupled to the cathode of diode 20, and the junction thereof is coupled to a terminal of opposite polarity of a reference source 25. The polarities of the reference sources 24 and 25 are changed during each half cycle so that from 0 to 7r the polarities of the sources are as indicated, and from 1r to 21r they are of reverse polarity. Reference sources 24 and 25 deliver equal but phase opposite signals to each diode pair. Resistors 28 and 29 are of equal ohmic value. Thus, for selection of in-phase components, diodes 20 and 21 conduct through resistors 26 and 27, during the first half cycle from 0 to 1r. Because of this conduction, the junction of resistors 26 and 27 experiences no voltage component due to the reference sources. However, due to the signal coming from input 1, the junction resistors 26 and 27 appear as a resistance equal to one half of resistor 26 or 27 and consequently the signal delivered to the amplifier 4 is attenuated. During the next half cycle, diodes 20 and 21 are non-conducting and no attenuation of the signal from input 1 occurs.

Asimilar action takes place on diodes 22 and 23 and resistors 28 and 29 as discussed above, except that this action occurs on the opposite half cycle to those above. While the invention has been disclosed in connection with specific embodiments, it is to be understood that variations and changes in the details may be made with- It is de sired, therefore, to be limited only as indicated by the scope of the appended claims.

I claim:

1. A phase discriminating circuit for selecting a desired phase component of an input signal including in combination first means for eliminating a predetermined portion of said input signal to produce a first output signal, means for applying said input signal to said first eliminating means, means comprising a series capacitor for removing the direct current component from said output signal to produce a periodic signal, means for applying the output signal to the removing means, second means for eliminating from the periodic signal the portion of said periodic signal corresponding to the portion of the input signal other than said predetermined portion and means for applying said periodic signal to the second eliminating means to produce an output wave form representative of the desired phase component.

2. A phase discriminating circuit as in claim 1 in which said first eliminating means eliminates a portion of said input signal corresponding to a half cycle of the input signal.

3. A phase discriminating circuit as in claim 1 in which said first and second eliminating means are respective alternately operated time-controlled impedances.

4. A phase discriminating circuit for selecting a desired phase component of an input signal including in combination first means for eliminating a predetermined portion of said input signal to produce a first output signal, means for applying said input signal to said first eliminating means, means comprising a series capacitor for removing the direct current component from said output signal to producea periodic signal, second means for eliminating the portion of said periodic signal corresponding to the portion of the input signal other than said predetermined portion, means for applying said periodic signal to the second eliminating means to produce an output wave form representative of the desired phase eliminating; means.

5. A phase discriminating circuit as in claim 4 in which said direct current removing means includes an input terminal and an output terminal, each of said eliminating means including an electron tube having a pair of electrodes, means connecting one of said electrodes to ground, means connecting the other of said electrodes to one of said terminals, said operating means including means for periodically rendering said electron tube conductive.

6. A phase discriminating circuit as in claim 4 in which said direct current component removing means includes an input terminal and an output terminal, each of said eliminating means including a pair of triodes having anodes and cathodes and grids, means connecting one of said anodes and one of said cathodes to one of said terminals, means connecting the other of said anodes and the other of said cathodes to ground, said operating means comprising means for applying a grid potential to said grids periodically to connect the associated terminal to ground.

7. A phase discriminating circuit as in claim 4 in which said direct current component removing means includes an input terminal and an output terminal, each of said eliminating means comprising a pair of diodes each having an anode and a cathode, said operating means including a source of electrical energy having a pair of terminals of opposite polarity and means for periodically reversing the terminal polarity, means connecting an anode and a cathode of the respective diodes of a pair to one of said terminals, means connecting the other anode and the other cathode of said pair to the respective source terminals, means connecting an anode and a cathode of the respective diodes of the other pair to the other terminal, and means connecting the other anode and cathode of said other pair to the respective source terminals.

References Cited in the file of this patent UNITED STATES PATENTS 2,511,671 Jacob June 13, 1950 2,625,662 Gaynor et al. Ian. 13, 1953 2,666,136 Carpenter Ian. 12, 1954 2,692,343 Spiro Oct. 19, 1954 2,762,978 Norton Sept. 11, 19 56 

